1. Field of the Invention
The present invention relates to a wear-resistant copper-base sintered oil-containing bearing material unlikely to mar an associated sliding shaft.
2. Prior Art
A sintered oil-containing bearing has a matrix alloy phase generally difficult to seize onto a shaft that is an associated member, includes therein an oil-containing hole for feeding a lubricating oil onto the sliding surface and may contain an additional solid lubricant, if required, to maintain lubrication during sliding.
Such sintered oil-containing bearing alloys based on copper and tin include one set forth in, for instance, Japanese Patent Publication No. 60-35978 issued in the name of the present applicant. This alloy is obtained through considerations on the influence of a matrix alloy and a solid lubricant upon the behavior of a sliding surface, and takes aim at preventing any plastic deformation of the matrix alloy by adding nickel or cobalt to the matrix alloy to impart increased toughness thereto, thereby allowing the solid lubricant to emerge effectively on the sliding surface to fulfill satisfactorily its lubricating function.
Specifically, this alloy is obtained by adding 1 to 20% of at least one of nickel and cobalt to a copper/tin-base material containing 2 to 15% of a solid lubricant.
The alloy provides a bearing material which is much more reduced in wear losses than a conventional copper/tin-base sintered oil-containing bearing to which a solid lubricant is added.
The alloy may be prepared by formulating electrolytic copper powders of 100 mesh or below in particle size and tin powders of 100 mesh or below as well as nickel or cobalt powders, molybdenum disulfide powders and lead powders, all of 200 mesh or below, into the above composition and forming and sintering the composition in ordinary manners.
With the matrix alloy reinforced, such a conventional sintered oil-containing bearing material as mentioned above tends to make a relatively strong attack on an associated shaft, so that it bites off and injures the shaft, ending up in an increase of the coefficient of friction.
Such a phenomenone does not occur in the case of shafts formed of quenched bearing steel or stainless steel and so offers no practical problem, but is found with those of carbon steel or stainless steel not heat-treated (hereinafter referred to as the green material).
Shafts formed of the green material are favorable in terms of cost and tend to be industrially used in combination with sintered oil-containing bearings. Thus, there is now still a demand for materials which make no attack on associated members.
Accomplished with the foregoing in mind, the present invention has for its object to eliminate such making-an-attack properties with respect to shafts of existing materials.